I'd think that Vizquel's great defensive play during the steroid era will prove to be viewed positively rather than negatively. Plenty of the old school voters - the purists and the players already in the HOF - hate the fact that steroid users now dominate the record books. Voting in a guy who played defense rather than hitting for 50+ home runs sends the message these old school guys want: Respect the game, play the right way.
I agree that the writers will think this way. Of course, this incorrectly assumes that steroids == hitting home runs. We have as many positive tests for Vizquel as we do for Bonds. Small guys like Alex Sanchez got busted, out of shape-looking guys like Rafael Betancourt too. And players in Smith's era (and before) were popping greenies left and right.
Also, while again I agree that the writers will think like you said, I think that defensive achievements should be scaled back some compared to the past. There are more at bats that result in home runs and strikeouts than there were 30 years ago, meaning it was more important (even if it was only worth a couple extra runs) back then to put out a good glove than it is today.
EDIT: And to make it clear, I'm not saying Vizquel shouldn't be in the Hall of Fame. But he wasn't Smith's equal offensively, and I can't stand the idea that we're just going to make random guesses on every player since Canseco came around, and ignore any drug problems MLB had before then. These will be the arguments used for Vizquel, but I think they're bad ones. There are good ones out there.